Genetic recombination of homologous DNA strands occurs following conjugation in E. coli. Such recombination seems to proceed by a set of pathways called RecBC, RecE and RecF after the genes whose products are thought to catalyze important steps. All the pathways use recA which catalyzes the central step in recombination (synpasis) and also can catalyze lengthening, possibly therefore stabilizing, the synaptic contact. A possible relationship between recF and recA products has been uncovered and part of this proposal is to study mutations in recA to see how they affect the activities of recA protein. Most of the proposal concerns the products of and the regulation of recE, recF and recJ, a new gene just recently discovered to be necessary for RecE and RecF pathways. Genetic molecular biological and enzymological methods will be employed to determine the role of these gene products in homologous recombination. The search for other genes of the RecE and RecF pathways is underway. Since homologous recombination is important in eukaryotes as well as prokaryotes exploration of the possible enzymatic identity of this process in such different organisms has begun. Not only is homologous recombination important in evolution of infectious bacteria, it is also involved in repair or circumvention of damage to DNA. Some of its enzymes are also involved in mutagenesis. Thus, study of this process may uncover information on DNA metabolism helpful in understanding diseases such as xeroderma pigmentosum, Fanconi's anemia and others which have been linked to abnormal repair processes.